1. Field of the Invention:
The present invention relates to an apparatus for simultaneously extracting various types of projection features of an image such as a character or any other figure, the apparatus being suitably applied to an image recognition apparatus such as an OCR (Optical Character Reader).
2. Description of the Prior Art:
A conventional image recognition apparatus for recognizing an image such as a character and any other figure is designed to perform processing utilizing mainly electronic techniques.
A conventional image recognition apparatus will be briefly described. An image pattern subjected to image recognition and written on an original by printing or the like is focused by an optical lens on a light-receiving surface of an image sensor comprising a CCD or a MOS sensor. A multi-value digital signal as image information is output from the image sensor and is binarized by a proper threshold value (if there are a plurality of multiple threshold values, multi-value conversion different from that described above is performed). The binarized signal is stored in a memory. The binarized image information is subjected to preprocessing for shaping the image, as needed. The preprocessed image information is stored in the above memory or another memory. Preprocessing includes noise reduction processing and normalization processing for positions, sizes, inclinations, and widths.
Subsequently, a projection feature required for discriminating an image is extracted by a projection-processing section from the image information stored in the memory.
In order to project an image on a given axis (e.g., the X-axis), the memory which stores the image information is scanned in a direction (e.g., the Y-axis) having a predetermined relationship with the given axis, and the image information is read out in time series or simultaneous time series. The readout image information is transferred to the projection-processing section. Pieces of the transferred image information are sequentially measured. Electric amounts sequentially obtained by such measurements are stored at predetermined positions in the memory or another memory corresponding to the given axis. A curve of an intensity distribution obtained by extracting projection features on the given axis is calculated on the basis of the stored electrical amounts.
The projection features of the image are normally extracted on a plurality of given axes, and thus a plurality of intensity distribution curves can be obtained about same information. The plurality of projection features of the image which are represented by these intensity distribution curves are compared with projection features of a prestored standard pattern, thereby discriminating the image.
In the image recognition apparatus described above, projection processing must be performed on a large number of axes about same image information in order to increase an image recognition rate, thereby extracting different types of projection features. In order to project an image on a large number of axes, one of the following procedures is required:
(1) The above-mentioned projection processing is repeated a number of times in a single projection-processing section; or
(2) A large number of projection-processing sections each having an independent memory for projection processing are prepared, and at the same time, pieces of image information read out from the memories for storing image information are transferred to the projection-processing sections. The above-mentioned projection processing operations are simultaneously performed in the large number of projection-processing sections.
In the conventional image recognition apparatus described above, processing is performed primarily employing electronic techniques. Processing time is inevitably prolonged as follows:
In order to increase the image recognition rate, projection features on a large number of axes must be extracted. However, in said procedure (1), the memory which stores the image information is scanned in a predetermined direction to sequentially read out the pieces of image information from the memory. These pieces of information are transferred to the projection-processing section and are measured sequentially as the electrical amounts in the projection-processing section. The intensity distribution curve must then be obtained on the basis of the electrical amounts obtained by such measuring. In addition, the above operation must be repeated a number of times and then the projection processing time will be prolonged, thus degrading efficiency of projection.
In said procedure (2), the intensity distribution curves are also obtained after the image information is transferred and measured. The projection processing time is prolonged, although said procedure (2) is not worse than said procedure (1). In this case a large number of projection-processing sections are required, and thus the overall system configuration is undesirably complicated.
In the conventional image recognition apparatus described above, if nonlinear projection processing such as circumferential or radial projection (to be described later) is performed, individual linear scanning start and end positions along a predetermined direction must be determined by a special function, and the range of a nonlinear pattern to be projected must be determined by a set of a large number of linear scanning cycles. Therefore, it is not easy to perform nonlinear projection of image information and thus it is very difficult to increase the image recognition rate.